Paper products containing wet strength resins

ABSTRACT

Disclosed are novel wet strength resins for paper, said resins being derived by reacting an epihalohydrin, such as epichlorohydrin, with a polyamino-copolyamide derived by reacting methylbisaminopropylamine with (a) a diester of oxalic acid and (b) a diester of a saturated dicarboxylic acid containing at least 4 carbon atoms, the mole ratio of (a) to (b) being from about 0.25:1 to about 10:1.

This application is a division of application Ser. No. 689,739, filedJan. 8, 1985, now U.S. Pat. No. 4,605,709, which is a continuation ofapplication Ser. No. 517,159, filed July 25, 1983, now abandoned, and isa continuation-in-part of application Ser. No. 488,894 filed Apr. 27,1983 abandoned.

This invention relates to a new wet and dry strength resin for paper.Particularly, this invention relates to a wet and dry strength resin foruse in the manufacture of paper, the broke of which can be easily andreadily repulped.

Broke is a waste product of the paper industry which, if not recoveredand utilized, represents a substantial loss. It is customary to repulpthe broke and reuse it in the papermaking process. Wet strength broke isdifficult to repulp and the repulping of wet strength broke is discussedby Schmalz in TAPPI, Vol. 44, pages 275-280 (April 1961).

It has been found that repulping of wet strength broke is facilitatedwhen the resin of this invention is employed in the manufacture of wetstrength paper.

Cationic, water-soluble, thermosetting resins derived by the reaction ofaminopolyamides with epichlorohydrin are known wet strength resins forpaper. Typical of these wet strength resins are the resins of U.S. Pat.No. 2,926,154 to Keim derived by the reaction of epichlorohydrin and anaminopolyamide produced from a polyalkylene polyamine and a C₃ to C₈saturated aliphatic dicarboxylic acid such as glutaric acid, adipic acidand the like. British Pat. No. 865,727 to Hercules Powder Co. and U.S.Pat. No. 3,311,594 to Earle, Jr. also disclose resins derived byreaction of epichlorohydrin and an aminopolyamide derived from a C₃ toC₁₀ saturated dicarboxylic acid and N-bis(aminopropyl)-methylamine, alsoknown as methylbisaminopropylamine. See also U.S. Pat. No. 3,793,279 toKipowski, U.S. Pat. No. 3,887,510 to Chan et al and U.S. Pat. No.3,891,589 to Ray-Chaudhuri which disclose the use of diesters derivedfrom C₂ to C₂₀ saturated dicarboxylic acids in the preparation ofaminopolyamides which are subsequently reacted with epichlorohydrin.Other U.S. patents which describe cationic, thermosetting, wet strengthresins for paper are U.S. Pat. Nos. 3,224,990; 3,240,664; 3,332,901 and3,700,623.

In accordance with this invention there is provided a new wet strengthresin. The new resin is derived by reacting an epihalohydrin, such asepichlorohydrin, with a polyaminocopolyamide derived by the reaction of(a) a diester of oxalic acid and (b) a diester of a saturated aliphaticdicarboxylic acid containing at least 4 carbon atoms withmethylbisaminopropylamine. The preferred diesters derived from oxalicacid are dimethyl oxalate, diethyl oxalate, and dipropyl oxalate. Thepreferred diesters of dicarboxylic acids contain 4 to 8 carbon atoms andmore preferably are the diesters of adipic and glutaric acid derivedfrom C₁ -C₃ saturated aliphatic monohydric alcohols such as methanol,ethanol, propanol, and isopropanol. Specific examples of the preferreddiesters are dimethyl adipate, diethyl adipate, dipropyl adipate,dimethyl glutarate, diethyl glutarate and dipropyl glutarate.

In the preparation of the resins of this invention the diestercomponents are first reacted with methylbisaminopropylamine to produce along chain polyamino-copolyamide. Methylbisaminopropylamine, alsoreferred to in the art as N-bis(aminopropyl)methylamine, has the formula##STR1## The polyamino-copolyamide is then reacted in aqueous solutionwith an epihalohydrin to form a water-soluble cationic thermosettingresin.

Reaction of the diester components with methylbisaminopropylamine ispreferably carried out neat but can also be carried out in a solution ofthe reactants in a suitable solvent such as an alcohol-water mixturecontaining, for example, equal parts of ethanol and water. The diesterof oxalic acid and the diester of the other dicarboxylic acid can beadded separately or simultaneously to the amine. Usually, the mole ratioof the diester of oxalic acid to the diester of the other dicarboxylicacid will range from about 0.25:1 to about 10:1, the preferred rangebeing from about 1:4 to about 4:1 and more preferably from about 1:3 toabout 3:1. Temperatures employed in the reaction can vary between about110° C. and about 225° C. and the preferred temperature range is about140° C. to about 200° C. Time of reaction depends on temperature and isinversely proportional thereto. Reaction time will vary from about 1/2to two hours.

In carrying out the reaction, it is preferred to use a total amount ofthe diesters sufficient to react substantially completely with theprimary amine groups of the methylbisaminopropylamine. This willususally require a mole ratio of amine to diesters of from about 0.9:1to about 1.2:1. The preferred mole ratio is about 1:1.

In converting the polyamino-copolyamide to a water-soluble cationicthermosetting resin, the polyamino-copolyamide is reacted in aqueoussolution with an epihalohydrin, preferably epichlorohydrin at atemperature from about 40° C. to about 100° C. and preferably from about45° C. to 85° C. until the viscosity of a 25% solids solution at 25° C.has reached about E-F or higher on the Gardner-Holdt scale. In thosecases where the free amine form of the polyamino-copolyamide has limitedwater solubility, the reaction is carried out using thepolyamino-copolyamide in the form of its water soluble acid salt. Theacid salt of the polyamino-copolyamide is easily and readily prepared byadding to an aqueous dispersion of the polyamino-copolyamide awater-soluble acid such as hydrochloric acid in an amount essentiallystoichiometrically equivalent to the tertiary amines of thepolyamino-copolyamide whereby essentially all the tertiary amines areconverted to the acid salt. Suitable acids for salt formation arewater-soluble, are within the skill of the art and include inorganicacids such as sulfuric acid, hydrochloric acid, nitric acid andphosphoric acid and organic acids such as acetic acid.

In the polyamino-copolyamide-epihalohydrin reaction, it is preferred touse sufficient epihalohydrin to convert all tertiary amine groups toquaternary ammonium groups.

Satisfactory resins can be prepared by using from about 1 mole to about1.5 moles and preferably from about 1.2 to about 1.4 moles ofepihalohydrin per mole of tertiary amine of the polyamino-copolyamide.pH adjustment is usually not necessary during reaction. However, sincethe pH decreases during the reaction it may be desirable in some casesto add alkali to combine with at least some of the acid formed. When thedesired viscosity is reached, sufficient additional water is added toadjust the solids content of the resin solution to about 15% or less andthe product cooled to room temperature, about 25° C. The resin willcontain a plurality of reactive ##STR2## groups

The resin is preferably stabilized against premature gelation byconverting essentially all the reactive ##STR3## groups to inactive##STR4## groups, x being the halogen of the epihalohydrin and chlorinewhen the epihalohydrin is epichlorohydrin.

The stabilization is accomplished by adding a water-soluble acid to theresin solution until essentially all the reactive groups are changed tothe inactive form. This is accomplished by adding sufficientwater-soluble acid to obtain and maintain a pH of from about 1 to 3. Thereactive groups are thereby changed to the inactive form and the resinsolution will be stabilized against gelation. When the pH remains at thedesired pH for a period of about one hour at room temperature (about 25°C.) it is relatively certain that the pH will not change and the resinsolution is stabilized against gelation. By this means, stable solutionshaving a resins solids content of from about 10% to about 50% can beprepared.

Acids that can be employed in the above stabilization procedure arewater-soluble acids such as hydrochloric acid, hydrobromic acid,hydrofluoric acid, hydroiodic acid, sulfuric acid, nitric acid,phosphoric acid and acetic acid. Mixtures of two or more water solubleacids can be used if desired.

Prior to use in the paper mill the stabilized resin is "reactivated" byadjusting the pH of the resin solution to and maintaining it above about8, preferably 10.5 and higher. Preferred pH range is 10.5 to 11. Thisreconverts essentially all the inactive ##STR5## groups to the reactivecross-linking ##STR6## groups. This pH adjustment is made by theaddition of a suitable organic or inorganic base such as the alkalimetal hydroxides and carbonates, calcium hydroxide,benzyltrimethylammonium hydroxide, and tetramethylammonium hydroxide.The alkali metals include sodium, potassium, cesium and lithium. Thebase is added preferably as an aqueous solution.

The polyamide-epichlorohydrin resins, prepared as herein described, maybe incorporated into pulp slurry at any point on the wet end of thepaper machine. However, prior to use, the stabilized resin must bereactivated as above set forth to convert the halohydrin groups toepoxide groups.

The resins of this invention exhibit high "off-the-machine" wet strengthand moderate to high dry strength. For most purposes, adequate wetstrength can be obtained by incorporating in the paper from about 0.2%to about 3% of the resin based on the dry weight of the pulp.

The invention is further illustrated by the following examples whichdemonstrate the best known embodiments of the invention. In theseexamples, intrinsic viscosity (I.V.) measurements were determined at 25°C. on a 2% solution in 1M ammonium chloride and Brookfield viscositymeasurements were determined at 25° C. using a #1 spindle at 60 r.p.m.unless otherwise indicated.

EXAMPLE 1

Part A--Methylbisaminopropylamine, 145.3 grams (1 mole) was charged to aresin kettle equipped with anchor stirrer, thermometer, heating mantle,nitrogen sparge and Dean-Stark water trap with condenser and the chargewas heated to 150° C. Dimethyl adipate, 43.55 grams (0.25 mole) anddiethyl oxalate, 109.6 grams (0.75 mole) were combined and addeddropwise keeping the temperature of the reaction mass between about 147°C. and about 150° C. After the addition was complete (about 1 hour) thetemperature of the reaction mass was allowed to rise to about 190°-195°C., the alcohol was collected and the reaction mixture was maintained at195° C. for a period of about 20 minutes. A very viscouspolyamino-copolyamide resulted which was poured into an aluminum pan.The yield of polyamino-copolyamide was 194 grams and it had an I.V. of0.141.

Part B--25.6 grams of the polyamino-copolyamide of Part A, 62.5 ml ofwater, and 11.75 grams of 37.5% aqueous HCl were thoroughly admixed toprovide a 28.9% aqueous solution of the resulting salt, the pH of thesolution being 4.65. 86.44 grams of the 28.9% aqueous solution (25grams, 0.1 mole of resin solids) were placed into a reaction vesseltogether with 44.5 ml of water and the pH of the solution was adjustedto 8.0 with 3.9 ml of 5 molar NaOH. Epichlorohydrin 11.6 grams (0.125mole) was added and the temperature of the resulting solution which wasat room temperature (about 25° C., was raised to 52°-72° C. and theviscosity of the solution monitored. When the Gardner-Holdt viscosityreached E, 220 ml of water was added and the pH was adjusted to 2 with10 molar HCl. Periodic pH adjustments were made until the pH of 2 wasconstant for about 60 minutes. The resulting solution had a solidscontent of 9.73% by weight and a Brookfield viscosity of 15 cps.

EXAMPLE 2

A 50:50 by weight mixture of Rayonier bleached kraft pulp andWeyerhaeuser bleached hardwood kraft pulp was beaten to CanadianStandard freeness of 500 cc in a Noble and Wood cycle beater. The pulpwas then adjusted to pH 7.5 with 10% NaOH and varying amounts, asspecified in Table 1, based on the dry weight of pulp, of thepolyamino-copolyamide-epichlorohydrin resin prepared in Example 1, wereadded. The solution of Example 1 was reactivated for use by diluting 25grams of the solution to about 3% solids with water, and adding, withmixing, 8.6 ml of 1N sodium hydroxide and 27.8 ml of water. Theresulting solution had a resin solids content of about 2% and a pH ofabout 11.7. The pulp was sheeted on a Noble and Wood handsheet machineto provide handsheets having a basis weight of approximately 40 poundsper ream (3000 square feet) and the resulting handsheets were wetpressed to a 33% solids content and then dried at 105° C. for 45 secondson a steam heated drum drier to 3-4% moisture. The dry strength wastested "uncured" (after 7 days of natural aging) or "cured" (after 30minutes at 80° C.). The sheets tested for wet strength were soaked fortwo hours in distilled water. Results are listed in Table 1.

                  TABLE 1                                                         ______________________________________                                        % of            Tensile Strength (lbs/inch)                                   Resin Basis     Dry           Wet                                             Added Weight    Uncured  Cured  Uncured                                                                              Cured                                  ______________________________________                                        0.25  40.6      21.3     21.8   3.15   3.26                                   0.50  40.1      22.4     22.0   3.89   4.07                                   0.75  40.4      23.3     23.9   4.72   5.01                                   --    39.9      18.9     19.0   0.58   0.62                                   ______________________________________                                    

EXAMPLE 3

Handsheets were prepared in accordance with the procedure of Example 2,using 0.7% resin based on the dry weight of the pulp. The handsheetsgave a dry tensile of 19.8 (uncured) and 19.7 (cured) and a wet tensileof 3.69 (uncured) and 4.02 (cured) pounds per inch at a basis weight of39.8 pounds per ream. Samples of these handsheets were repulped inaqueous NaOH at a pH of about 12 and at a temperature of about 85° C.Repulping of the paper sheets was carried out according to TAPPI method205 m-58 at a mixer speed of 2800 r.p.m., a pulp consistency of 1.3% anda pH of 12. The degree of repulping (fiber separation) was measured andreported in integers ranging from 1-6, the integer 6 indicatingsubstantially complete repulping. After 20 minutes, the degree ofrepulping was measured at 5 and after 30 minutes there was substantiallycomplete repulping.

EXAMPLE 4

Part A--The procedure of Example, 1 Part A was repeated except that 87.1grams (0.5 mole) of dimethyl adipate and 73.1 grams (0.5 mole) ofdiethoxyalate were used. The yield of polyamino-copolyamide was 205grams and it had an I.V. of 0.146.

Part B--27.25 grams of the polyamino-copolyamide of Part A, 64 ml ofwater and 11.75 grams of 37.5% HCl were thoroughly mixed to provide a29.5% aqueous solution of the resulting salt, the pH of the solutionbeing 4.45. 84.7 grams of the 29.5% aqueous solution (25 grams, 0.095mole of resin solids) were placed in a reaction vessel with 43 ml ofwater and the pH was adjusted to 8.1 with 4.45 ml of 5 molar NaOH.Epichlorohydrin, 10.9 grams (0.118 mole) was added and the temperatureof the resulting solution was raised to 67°-72° C. and the viscosity ofthe solution was monitored. When the Gardner-Holdt viscosity reachedE-F, 2.5 ml of water were added and the pH was adjusted to 2 with 10molar HCl. Periodic pH adjustments were made until the pH was constantfor about 60 minutes. The resulting solution had a solids content of9.62% and a Brookfield viscosity of 19.4 cps.

EXAMPLE 5

Part A--The procedure of Example 1, Part A was repeated except that130.7 grams (0.75 mole) of dimethyl adipate and 36.5 grams (0.25 mole)of diethyl oxalate were used. The polyamino-copolyamide had an I.V. of0.137.

Part B--28.9 grams of the polyamino-copolyamide of Part A, 70.4 ml ofwater and 11.75 grams of 37.5% HCl were thoroughly mixed to provide a29.13% aqueous solution of the resulting salt, the pH of the solutionbeing 4.3. 95.7 grams of the 29.13% aqueous solution (27.9 grams, 0.10mole of resin solids) were placed in a reaction vessel with 47 ml ofwater and the pH was adjusted to 8.1 with 4 ml of 5 molar NaOH.Epichlorohydrin, 11.6 grams (0.125 mole) was added and the temperatureof the resulting solution was raised to 69°-72° C. and the viscosity ofthe solution was monitored. When the Gardner-Holdt viscosity reachedE-F, 237 ml of water were added and the pH was adjusted to 2 with 10molar HCl. Periodic pH adjustments were made until the pH was constantfor about 60 minutes. The resulting solution had a solids content of9.73% and a Brookfield viscosity of 17 cps.

EXAMPLE 6

Part A--The procedure of Example 1, Part A was repeated except that 40.1grams (0.25 mole) of dimethyl glutarate were substituted for the 43.55grams of dimethyl adipate. The yield of polyamino-copolyamide was 185grams and it had an I.V. of 0.161.

Part B--25.1 grams of the polyamino-copolyamide of Part A, 61.4 ml ofwater and 11.75 grams of 37.5% HCl were thoroughly mixed to provide a29.22% aqueous solution of the resulting salt, the pH of the solutionbeing 6.5. 85.56 grams of the 29.22% aqueous solution (25.0 grams, 0.101mole of resin solids) were placed in a reaction vessel with 46 ml ofwater and the pH was adjusted to 8.05 with 3.3 ml of 5 molar NaOH.Epichlorohydrin, 11.6 grams (0.125 mole) was added and the temperatureof the resulting solution was raised to 65°-71° C. and the viscosity ofthe solution was monitored. When the Gardner-Holdt viscosity reachedE-F, 220 ml of water were added and the pH was adjusted to 2 with 10molar HCl. The resulting solution had a solids content of 9.7% and aBrookfield viscosity of 19.2 cps.

EXAMPLE 7

Part A--The procedure of Example 4, Part A was repeated except that 80.1grams (0.5 mole) of dimethyl glutarate were substituted for the 87.1grams of dimethyl adipate. The yield of polyamino-copolyamide was 197grams and it had an I.V. of 0.152.

Part B--26.4 grams of the polyamino-copolyamide of Part A, 64.5 ml ofwater and 11.75 grams of 37.5% HCl were thoroughly mixed to provide a29.2% aqueous solution of the resulting salt, the pH of the solutionbeing 6.65. 85.58 grams of the 29.2% aqueous solution (25.0 grams, 0.098mole of resin solids) were placed in a reaction vessel with 45.8 ml ofwater and the pH was adjusted to 8.0 with 2.1 ml of 5 molar NaOH.Epichlorohydrin, 11.3 grams (0.123 mole) was added and the temperatureof the resulting solution was monitored. When the Gardner-Holdtviscosity reached E-F, 362 ml of water were added and the pH wasadjusted to 2 with 10 molar HCl. The resulting solution had a solidscontent of 9.7% and a Brookfield viscosity of 17.5 cps.

EXAMPLE 8

Part A--The procedure of Example 5, Part A was repeated except that120.2 grams (0.75 mole) of dimethyl glutarate were substituted for the130.7 grams of dimethyl adipate. The polyamino-copolyamide had an I.V.of 0.141.

Part B--27.7 grams of the polyamino-copolyamide of Part A, 67.5 ml ofwater and 11.75 grams of 37.5% HCl were thoroughly mixed to provide a28.57% aqueous solution of the resulting salt, the pH of the solutionbeing 6.6. 87.5 grams of the 28.57% aqueous solution (25.0 grams, 0.098mole of resin solids) were placed in a reaction vessel with 42 ml ofwater and the pH was adjusted to 8.0 with 2.3 ml of 5 molar NaOH.Epichlorohydrin, 10.8 grams (0.117 mole) was added and the temperatureof the resulting solution was raised to 63°-76° C. and the viscosity ofthe solution was monitored. When the Gardner-Holdt viscosity reachedE-F, 215 ml of water were added and the pH was adjusted to 2 with 10molar HCl. The resulting solution had a solids content of 9.7% and aBrookfield viscosity of 18 cps.

EXAMPLES 9 TO 13

The resin solutions of Examples 4 to 8 were activated for use using theprocedure set forth in Example 2, and paper sheets were prepared usingthe resulting solutions and tested in accordance with the procedure ofExample 2. Strength properties of the sheets are set forth in Table IIbelow.

                  TABLE II                                                        ______________________________________                                               Addi-         Tensile Strength (lbs/inch)                              Re-      tion            Dry       Wet                                        Ex.   sin    % of    Basis Un-         Un-                                    No.   of     Pulp    Weight                                                                              cured Cured cured Cured                            ______________________________________                                         9    Ex. 4  0.25    40.5  21.8  21.2  2.70  2.73                                          0.50    40.5  21.9  22.8  3.91  3.96                                          0.75    40.2  21.3  22.2  4.37  4.34                             10    Ex. 5  0.25    40.5  21.5  21.7  2.46  2.57                                          0.50    40.2  20.9  21.3  3.12  3.15                                          0.75    39.9  21.2  21.4  3.56  3.80                             11    Ex. 6  0.25    39.9  20.7  21.8  3.04  3.17                                          0.50    40.1  21.5  22.6  3.61  4.09                                          0.75    40.0  22.4  22.9  4.47  4.75                             12    Ex. 7  0.25    40.3  21.3  21.1  3.00  3.16                                          0.50    40.2  22.5  21.0  3.67  3.95                                          0.75    40.3  22.8  22.9  4.40  4.69                             13    Ex. 8  0.25    40.0  20.8  20.9  2.67  2.90                                          0.50    40.3  21.2  20.3  3.44  3.15                                          0.75    41.1  21.4  21.4  3.96  4.26                             Blank --     --      39.9  18.9  19.0  0.58  0.62                             ______________________________________                                    

EXAMPLES 14 TO 16

Paper sheets were prepared in accordance with the method of Example 2using an amount (based on dry pulp) of the resins of Examples 4, 6 & 7to provide uncured sheets of substantially equivalent wet strength. Thestrength properties of these sheets are set forth in Table III.

                  TABLE III                                                       ______________________________________                                               Addi-         Tensile Strength (lbs/inch)                              Re-      tion            Dry       Wet                                        Ex.   sin    % of    Basis Un-         Un-                                    No.   of     Pulp    Weight                                                                              cured Cured cured Cured                            ______________________________________                                        14    Ex. 4  0.8     40.0  19.9  19.3  3.72  3.94                             15    Ex. 6  0.75    40.1  19.3  20.0  3.64  3.85                             116   Ex. 7  0.75    40.1  20.0  20.5  3.80  3.90                             Blank --     --      39.9  17.8  18.0  0.60  0.59                             ______________________________________                                    

The paper sheets were repulped in aqueous NaOH at a pH of about 12 and atemperature of about 85° C. The degree of repulping was measured at 5and 10 minutes and then every 10 minutes up to a total of 1 hour (oruntil stage 6, essentially complete fiber separation was reached) usingthe method set forth in Example 3. Test results are set forth in TableIV below.

                  TABLE IV                                                        ______________________________________                                                 Degree of Repulping (After Minutes)                                  Example No.                                                                              5        10        20    30                                        ______________________________________                                        14         <1       3         5     6                                         15         1        3         5     6                                         16         1        3         5     6                                         ______________________________________                                    

EXAMPLES 17 TO 19

Polyamino-copolyamides were prepared according to the procedures ofExamples 6 to 8, Part A and 0.10 mole of each of the resultingpolyamino-copolyamides, as its acid salt solution, was reacted with0.125 mole of epichlorohydrin at a solids content of 25%, a pH of 8.0and a temperature of 65°-77° C. until the Gardner-Holdt viscosityreached E to F, after which time the resin solution was diluted withwater and the pH was adjusted to 1-2 according to the general procedureof Example 1, Part B.

For the sake of comparison, a control resin was also prepared as aboveexcept that the polyamino-polyamide was formed by reacting 1 mole ofmethylbisaminopropylamine with 1 mole of dimethyl glutarate at 180°-190°C. for 1 hour.

The resin solutions prepared above were activated and used to preparepaper sheets in accordance with the procedure of Example 2. Details ofthese examples and the control are set forth in Table V and the strengthproperties of the paper sheets are set forth in Table VI, below.

                  TABLE V                                                         ______________________________________                                                      Ex.   Ex.     Ex.                                                             17    18      19      Control                                   ______________________________________                                        Reactants (moles)                                                             methylbisaminopropylamine                                                                     1.0     1.0     1.0   1.0                                     diethyl oxalate 0.75    0.50    0.25  --                                      dimethyl glutarate                                                                            0.25    0.50    0.75  1.0                                     Intrinsic Viscosity                                                                           0.161   0.152   0.141 0.132                                   of polyamide                                                                  Resin Solution                                                                Total Solids (%)                                                                              8.9     9.2     9.4   9.1                                     Brookfield Viscosity (cps)                                                                    20.7    16.8    16.4  17.0                                    ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                        Addition           Tensile Strength (lbs/inch)                                Ex.   % of     Basis   Dry        Wet                                         No.   Pulp     Weight  Uncured.sup.1                                                                        Cured Uncured.sup.1                                                                        Cured                              ______________________________________                                        17    0.25     40.5    19.9   21.6  2.84   4.01                                     0.50     40.4    21.7   23.0  4.24   5.31                                     0.75     40.7    22.7   24.7  4.79   5.64                               18    0.25     40.2    20.9   21.7  3.15   3.95                                     0.50     40.2    20.8   22.7  3.99   5.00                                     0.75     40.7    22.2   24.4  4.57   5.64                               19    0.25     40.9    19.6   20.3  2.68   3.14                                     0.50     40.8    19.5   22.6  3.41   4.08                                     0.75     40.5    22.0   21.8  3.83   5.15                               Con-  0.25     40.3    19.8   21.6  2.39   3.21                               trol  0.50     40.8    20.1   21.5  3.07   3.82                                     0.75     41.1    20.5   21.8  3.57   4.71                               Blank --       40.6    18.0   19.1  0.48   0.61                               ______________________________________                                         .sup.1 after 5 days of natural aging                                     

EXAMPLES 20 TO 22

Paper sheets were prepared in accordance with the method of Example 2using an amount (based on dry pulp) of the resins of Examples 17 to 19and the control to provide uncured sheets of substantially equivalentwet strength. The strength properties of these sheets are set forth inTable VII.

                  TABLE VII                                                       ______________________________________                                        Ex.    Resin    % Resin  Basis Wet Tensile Strength                           No.    of       Added    Weight                                                                              lbs/inch, uncured                              ______________________________________                                        20     Ex. 17   0.75     40.5  4.36                                           21     Ex. 18   0.80     40.0  4.40                                           22     Ex. 19   1.00     40.1  4.05                                           Control                                                                              Control  1.00     40.5  3.64                                           Blank  --       --       40.2  0.55                                           ______________________________________                                    

The paper sheets were repulped in aqueous NaOH at a pH of about 12 and atemperature of about 85° C. The degree of repulping was measured in themanner of Examples 14 to 16 and the results are set forth in Table VIII.

                  TABLE VIII                                                      ______________________________________                                        Example                                                                              Degree of Repulping (After Minutes)                                    No.    5       10      20    30   40    50   60                               ______________________________________                                        20     <1      2       5     6                                                21     1       2       5     6                                                22     1       2       4     5    6                                           Control                                                                              <1      <1      1     2    3     3    4                                ______________________________________                                    

It is to be understood that the resin solutions prepared in accordancewith this invention can be used to impart wet and dry strength to paperwithout first being stabilized against premature gelation followed byreactivation with base. Thus, if the resin solution is to be usedpromptly there is no need to go through the stabilization andreactivation steps. However, as is usually the case, the resin solutionwill be stored for a period of time prior to use, during which timepremature gelation can occur. Thus, it is recommended that pH adjustmentto insure against premature gelation be made during the manufacturingprocess.

The above description and working examples are illustrative of thisinvention and not in limitation thereof.

What I claim and desire to protect by Letters Patent is:
 1. A paperproduct having wet and dry strength and improved repulpabilitycomprising sheeted cellulose fibers treated with from about 0.2 to about3% by weight, based on dry weight of fibers, of a water-soluble,cationic thermosetting resin derived by reactingmethylbisaminopropylamine with (a) a diester of oxalic acid and (b) adiester of a saturated aliphatic dicarboxylic acid containing at least 4carbon atoms to form a polyamino-copolyamide containing tertiary aminegroups, the mole ratio of (a) to (b) being from about 0.25:1 to about10:1 and the mole ratio of methylbisaminopropylamine to the diestersbeing from about 0.9:1 to about 1.2:1 and then reacting thepolyamino-copolyamide, in aqueous solution with from about 1 mole toabout 1.5 moles of epihalohydrin per mole of tertiary amine groupspresent in said polyamino-copolyamide.
 2. The paper product of claim 1,wherein the epihalohydrin is epichlorohydrin.
 3. The paper product ofclaim 2, wherein the dicarboxylic acid contains 4 to 8 carbon atoms. 4.The paper product of claim 2, wherein the mole ratio of (a) to (b) isfrom about 1:4 to about 4:1.
 5. The paper product of claim 4, whereinthe dicarboxylic acid is glutaric acid or adipic acid.
 6. The paperproduct of claim 5, wherein the diester of oxalic acid is diethyloxalate.
 7. The paper product of claim 6, wherein the diester ofglutaric acid or adipic acid is the dimethyl ester.